1. Field of the Invention
The present invention relates to formulations of calcium fortified acidic beverages that are stable against calcium precipitation when stored for prolonged period at room temperature and elevated temperatures.
2. Description of Related Art
Calcium is the most abundant mineral in the body and is a major constituent of bone and teeth. Calcium is also involved in several physiological systems such as blood clotting, increasing cell membrane permeability, activating a number of enzymes, and acting as component in neural transmission and muscular contraction. Calcium deficiency may be a factor in the development of osteoporosis in elderly people.
Since the body does not produce calcium, it is totally dependent on external supply of calcium, which is nutritional or supplementary. Calcium may be obtained from various dietary sources, of which the primary sources are dairy products, in particular milk. Milk, however, is not generally consumed in sufficient quantities by the general population to obtain needed levels of calcium. One reason is that milk may be unattractive as a drink for social occasions. Also, a significant number of individuals are lactose intolerant, resulting in gastrointestinal problems if milk is consumed.
To increase the consumption of calcium, a more appealing alternative to milk is apparently needed. Beverages, which are consumed often by the general public, have been used as a vehicle for achieving greater calcium intake. Calcium supplementation in beverages, however, has been generally limited to liquid beverages of short shelf lives requiring refrigeration. For example, Sunny Delight® Orange with Calcium of Procter and Gamble, Cincinnati, Ohio, USA, contains calcium citrate malate and is labeled as being protected by U.S. Pat. No. 4,737,375. Tropicana® Orange with Calcium of Tropicana Products, Inc., Bradenton, USA, also contains calcium citrate malate and is labeled as being protected by U.S. Pat. No. 4,722,847. Minute Maid® Orange with Calcium of the Coca-Cola Company, Houston, Tex., USA, contains calcium lactate and tricalcium phosphate according to U.S. Pat. No. 4,871,554.
Short shelf-life natural fruit beverages requiring refrigeration are normally pasteurized at about 75° C. to preserve the flavor. Aseptic pasteurization at higher temperature, normally 95° C., allows natural fruit beverages to be stored longer and without refrigeration, but with consequent loss in flavor quality. Aseptic pasteurization is performed on other acidic beverages such as tea, cola, and those containing artificial or nature-identical flavors. These long shelf-life acidic beverages are packed in bottles and aseptic cartons, and normally have shelf lives of 5–10 months without refrigeration.
It is extremely difficult to fortify long shelf-life acidic beverages with calcium because of their organic acids, in particular citric and/or malic acid, which are naturally present in most fruits or added in artificially flavored beverages for sourness. When a soluble salt of calcium is added to get a clear beverage, the calcium eventually forms calcium citrate or calcium malate, which because of their poor solubility precipitate out of solution. The formation of the precipitate is generally faster at higher temperature, making it more difficult to fortify acidic beverages that do not require refrigeration.
Further, when highly soluble salts of calcium are used, undesirable taste becomes a problem. For example, calcium acetate tastes vinegary, calcium chloride salty. Insoluble calcium salts cannot be used since they sediment rapidly out of solution making the product aesthetically unpleasant, and which may lead to incomplete intake of the added calcium. Emulsification of insoluble calcium salts by surfactants can lead to off-taste and opacity that is aesthetically undesirable for acidic beverages.
It has been found that organic salts of calcium are generally more bioavailable than the inorganic salts. For example, U.S. Pat. Nos. 4,772,467 and 5,128,374 teach the use of calcium citrate and calcium citrate malate, respectively, to treat osteoporosis. Calcium citrate and calcium malate are fairly insoluble and their direct use in liquid beverages can lead to problems previously described with insoluble calcium salts. However, calcium citrate can be formed in-situ by reacting a fairly insoluble calcium base selected from calcium carbonate, calcium oxide, and calcium hydroxide with citric acid as described in U.S. Pat. No. 4,851,221. The calcium citrate thus formed is in a metastable state, which eventually precipitates to the low equilibrium solubility of calcium citrate. As mentioned previously, precipitation generally occurs faster at higher temperature making it difficult or almost impossible to incorporate in-situ formed calcium citrate, calcium malate, and calcium citrate malate that is resistant to precipitation for at least five months at room temperature, and at least two months at 50° C. to ensure the product survives spikes of high temperature during transport and warehouse storage. In tropical countries, it is not unusual for a warehouse with ambient cooling to reach temperatures of up to 40° C.
In-situ formed calcium citrate, calcium malate, and calcium citrate malate are good calcium sources for acidic beverages since they blend very well with fruit flavors and iced tea, without the chalky aftertaste of calcium. The prior art does not teach how these calcium sources can be stabilized against precipitation in long shelf-life acidic beverages not requiring refrigeration.